Fluorinated Gold Nanoparticles for Nanostructure Imaging Mass Spectrometry

Nanostructure
imaging mass spectrometry (NIMS) with fluorinated
gold nanoparticles (f-AuNPs) is a nanoparticle assisted laser desorption/ionization
approach that requires low laser energy and has demonstrated high
sensitivity. Here we describe NIMS with f-AuNPs for the comprehensive
analysis of metabolites in biological tissues. F-AuNPs assist in desorption/ionization
by laser-induced release of the fluorocarbon chains with minimal background
noise. Since the energy barrier required to release the fluorocarbons
from the AuNPs is minimal, the energy of the laser is maintained in
the low μJ/pulse range, thus limiting metabolite in-source fragmentation.
Electron microscopy analysis of tissue samples after f-AuNP NIMS shows
a distinct “raising” of the surface as compared to matrix
assisted laser desorption ionization ablation, indicative of a gentle
desorption mechanism aiding in the generation of intact molecular
ions. Moreover, the use of perfluorohexane to distribute the f-AuNPs
on the tissue creates a hydrophobic environment minimizing metabolite
solubilization and spatial dislocation. The transfer of the energy
from the incident laser to the analytes through the release of the
fluorocarbon chains similarly enhances the desorption/ionization of
metabolites of different chemical nature, resulting in heterogeneous
metabolome coverage. We performed the approach in a comparative study
of the colon of mice exposed to three different diets. F-AuNP NIMS
allows the direct detection of carbohydrates, lipids, bile acids,
sulfur metabolites, amino acids, nucleotide precursors as well as
other small molecules of varied biological origins. Ultimately, the
diversified molecular coverage obtained provides a broad picture of
a tissue’s metabolic organization.